Gallery not editable

I have created a field to upload multiple images to a gallery using Pods’ File/Image/Video field.

The images upload fine, and display fine, but if I want to change the gallery and delete a given image the deleted image is still visible on the front end.

I must be doing something wrong, but I’ve tried it by making a custom post type, as well as simply extending the regular post, but I get the same issue.

Thanks